Minimally invasive surgery offers many benefits over traditional open surgery techniques, including less pain, shorter hospital stays, quicker return to normal activities, minimal scarring, reduced recovery time, and less injury to tissue. Consequently, demand for minimally invasive surgery using robotic surgical systems is strong and growing.
Laparoscopy is a type of minimally invasive surgery in which a small incision is made in the abdominal wall through which an instrument called a laparoscope is inserted to permit anatomic structures within the abdomen and pelvis to be seen. The abdominal cavity is commonly distended and made visible by the instillation of absorbable gas such as carbon dioxide. Tubes may be pushed through the same or different incisions in the skin so that probes or other instruments can be introduced to a surgical site. In this way, a number of surgical procedures can be performed without the need for a large or open cavity surgical incision.
One disadvantage of laparoscopy, however, is the inability to manually palpate hidden or solid organs. Laparascopic Ultrasound (“LUS”) allows the surgeon to overcome this limitation by providing visualization of deeper structures. In fact, even when open cavity operations are performed, intraoperative ultrasonography may be significantly more sensitive at detecting otherwise occult lesions within anatomic structures than bimanual palpation.
As an example, intraoperative ultrasonography of the liver is useful in a variety of clinical settings during laparoscopic surgery. These include: staging and assessment of the liver, including ultrasound-guided needle biopsy, liver tumor ablation, and evaluation of the liver prior to laparoscopic liver resection.
For resection procedures, surgeons should have the ability to perform accurate staging of the liver and other sites to rule out metastatic disease prior to resection. The addition of LUS to standard laparoscopy improves the diagnosis of metastases over conventional preoperative diagnostic methods.
Ultrasound-directed liver biopsy is an important component of hepatic staging and assessment. When a lesion is identified by ultrasound, needle biopsy is necessary to confirm the findings histologically. Current practice requires manual free-hand LUS in conjunction with free-hand positioning of the biopsy needle under ultrasound guidance.
For the treatment of unresectable metastases, increasing interest has been focused on ablative approaches such as radiofrequency (“RF”), cryotherapy, microwave, or chemical ablation. While interstitial ablation can be performed percutaneously or during open surgery, laparoscopic ablation has significant advantages. First, unlike percutaneous therapy, laparoscopy can identify both hepatic and extrahepatic metastases not visualized on preoperative imaging, which misses significant tumors in about 10% to 20% of patients with colorectal liver metastases. Second, laparoscopic or operative ultrasound (“US”) has been shown to be significantly more accurate than transabdominal US, CT or MR at visualizing liver lesions. Further, operative approaches, including laparoscopy, permit mobilization of structures away from a surface tumor that may be thermally injured during RF ablation. Percutaneous ablation and laparoscopic ablation both typically require general anesthesia and an overnight hospital stay. Laparoscopy, on the other hand, does not impose a significantly greater burden on the patient.
While ablation promises advantages compared to other approaches, the technical difficulty of manipulating the ultrasound probe, aligning the ultrasound probe with the ablation probe, and placement of the ablation probe demands considerable expertise. The surgeon must precisely place the ablation probe tip within the volumetric center of the tumor in order to achieve adequate destruction of the tumor and a 1 cm zone of surrounding normal parenchyma. Tumors are identified by preoperative imaging, primarily CT and MR, and then laparoscopically localized by LUS.
One major limitation of ablative approaches is the lack of accuracy in probe tip placement within the center of the tumor. This is particularly important, as histologic margins cannot be assessed after ablation as is done with hepatic resection. In addition, manual guidance often requires multiple passes and repositioning of the probe tip, further increasing the risk of bleeding and tumor dissemination. Intraoperative ultrasound provides excellent visualization of tumors and provides guidance for RF probe placement, but its 2D-nature and dependence on the sonographer's skill limit its effectiveness.
Although laparoscopic instrumentation and techniques are beginning to be extended to resection of the liver, loss of the surgeon's tactile sense makes it difficult to assess the safe margins of resection necessary for safe parenchymal transection. Lack of clear visualization and mapping of intrahepatic structures with current LUS techniques could result in catastrophic injury to major adjacent structures. The surgeon must carefully examine the liver by ultrasound prior to resection in order to rule out additional tumors which may preclude curative therapy. Surgeons also require ultrasound to determine and plan safe and complete resection with sufficient surgical margin clearance.
Despite its theoretical advantages, intraoperative LUS is not widely practiced for such uses as laparoscopic liver cancer surgery. To expand usage in this and other applications, advances in LUS robotic surgical systems that improve surgeon efficiency in performing minimally invasive surgical procedures, as well as the ease of using those systems is desirable.
For example, optimization of LUS for hepatic surgery may significantly improve the clinical management of patients. In addition to minimizing morbidity and discomfort, an improved LUS robotic surgical system may significantly reduce costs. Faster, more accurate, and more complete assessment of the liver may be performed by experts, as well as potentially by surgeons who are not experts in intraoperative ultrasonography of the liver.
Image-guided biopsy of sometimes small and inaccessible liver lesions may be facilitated. Advanced LUS robotic tools could increase the use of resection as a definitive treatment for larger and less favorably placed tumors. Improved real-time guidance for planning, delivery and monitoring of ablative therapy may also provide the missing tool needed to allow accurate and effective application of this promising therapy.